The present invention is directed generally to a combined global positioning system receiver and radio unit and, more particularly, to a system and method for transmitting position information between a plurality of such units so that one unit can display the position of one or more other units.
A global positioning system (GPS) is an electronic satellite navigation system which permits a user of the system to determine his or her position with respect to the Earth. Global positioning is accomplished through the use of a handheld GPS receiver device which detects and decodes signals from a number of satellites orbiting the Earth. The signals from each of these satellites indicate the position of the satellite and the time at which the signal was sent. To decode the satellite signals, known as spread spectrum signals, and thereby calculate the desired navigational data, a GPS receiver must first xe2x80x9cfindxe2x80x9d or acquire the signals emitted from a minimum number of satellites. Once the receiver is xe2x80x9clocked onxe2x80x9d to the spread spectrum signals, continuous real-time calculation and monitoring of the user""s global position and other navigational data (e.g., velocity of movement) can be performed.
GPS receivers have clocks which are synchronized with clocks in each of the satellites to determine how long it takes the signals to travel from the satellites to the receiver. In this regard, GPS receivers require a highly accurate internal frequency reference in order to acquire the spread spectrum GPS satellite signals. Specifically, acquiring spread spectrum satellite signals from a sufficient number of satellites to perform calculations requires determining the frequency of oscillation of the crystal oscillator utilized in the GPS receiver.
Once the GPS receiver has acquired and decoded signals from a minimum of three satellites, the GPS receiver can calculate the user""s position (i.e., latitude and longitude) by geometric triangulation. Upon acquiring signals from a minimum of four satellites, the GPS receiver can also calculate the user""s altitude. In addition, GPS receivers are able to calculate the user""s speed and direction of travel by continuously updating the user""s position. Accordingly, GPS receivers are highly valuable and widely used in navigational systems because of their ability to accurately compute the user""s position on or near the Earth in real-time, even as the user is moving.
In addition to the growing popularity and demand for GPS navigational devices, portable two-way radios continue to enjoy widespread popularity. In 1996, the Federal Communications Commission (FCC) established the Family Radio Service (FRS) so that families and other small groups could communicate with one another over very short distances (typically less than one mile) at no charge and without an FCC license. The FRS, which is one of the Citizens Band Radio Services, includes 14 channels in the UHF 460 MHz band. There are a number of commercially available two-way radios which are designed for use with the FRS. The increasing use of both portable radios and global positioning systems has led to proposals to incorporate GPS receivers into portable radio devices.
Notwithstanding the many recent technological advancements in GPS and wireless radio equipment, and increased applications for those technologies, there is not currently a combined portable GPS/radio unit capable of displaying the location of another GPS/radio unit. Likewise, there is not currently a combined portable GPS/radio unit capable of displaying the location of multiple GPS/radio units.
It is an object of the present invention to provide a combined GPS/radio unit which is capable of displaying the location of at least one other such unit.
Another object of the present invention is to provide a combined GPS/radio unit which is capable of displaying its location and the location of at least one other such unit.
A further object of the present invention is to provide a combined GPS/radio unit which displays the location of another unit together with an identifier for that unit.
Still another object of the present invention is to provide a system in which a plurality of portable units communicate with one another over a wireless radio network and at least one of the units displays the location of other units.
Yet another object of the present invention is to provide a method for displaying the location of a first portable GPS/radio unit on a second portable GPS/radio unit.
These and other related objects of the present invention will become readily apparent upon further review of the specification and drawings. To accomplish the objects of the present invention, a portable GPS/radio unit is provided which is capable of communicating with one or more other such units over a wireless radio network, wherein each of the other units is adapted to transmit radio signals over the network indicative of that unit""s location. The GPS/radio unit comprises a GPS receiver for receiving satellite signals from a plurality of satellites, a processor coupled with the GPS receiver for calculating the location of the GPS/radio unit as a function of the received satellite signals, and a radio receiver coupled with the processor for receiving the radio signals transmitted by said other units. The processor is adapted to identify the location of the other units based on the received radio signals. The GPS/radio unit also includes a display for indicating the location of at least one of the other units.
In another aspect of the present invention, a system is provided in which a plurality of portable GPS/radio units communicate with one another over a wireless radio network. The system comprises a first portable GPS/radio unit which has a GPS receiver for receiving satellite signals from a plurality of satellites, a processor for calculating the location of the first unit as a function of the received satellite signals, and a radio transmitter for transmitting radio signals indicative of the location of said first unit. The system further comprises a second portable GPS/radio unit having a GPS receiver for receiving satellite signals from a plurality of satellites, a processor for calculating the location of the second unit as a function of the received satellite signals, a radio receiver for receiving radio signals from one or more other portable units, and a display for indicating the location of the other portable units. Upon receiving radio signals indicative of the location of the first unit, the processor of the second unit identifies the location of the first unit based on the received radio signals.
In still another aspect of the present invention, a method is provided for displaying the location of a first portable GPS/radio unit on a second portable GPS/radio unit. The method comprises receiving a first set of satellite signals from a plurality of satellites at a first portable GPS/radio unit, calculating the location of the first unit as a function of the first set of received satellite signals, receiving a second set of satellite signals from a plurality of satellites at a second portable GPS/radio unit, calculating the location of the second unit as a function of the second set of received satellite signals, transmitting the location of the first unit to the second unit over a wireless radio network, and displaying the location of the first unit on the second unit.